The Identification Of Density-tolerance And Genetic Study Of Maize Underdifferent Density Selection Pressure

The breeding methods of maize inbred lines,inbred lines and hybrids resistant identification,heterosis, combining ability and genetic parameters under different density selection pressure were studied in this paper,what included four aspects.The first, we selected six inbred lines from domesitic maize group which were zheng58, Mo17, Chang7-2, Dan340, PH6WCand PH4CVand Researched their density-tolerance, stress tolerance and the best density under seven densities,60000plants/hm2,75000plants/hm2,90000plants/hm2,110000plants/hm2,130000plants/hm2, respectively.The second, we selected nine hybird including JNY986, JNY611, JNY886, JNY503, JNY787, xianyu335, zhengdan958and dika516. The density-tolerance and selection of the best density under seven densities, respectively,30000plants/hm2,45000plants/hm2,60000plants/hm2,75000plants/hm2,90000plants/hm2,110000plants/hm2,130000plants/hm2were researched. The third, PHB1M×chang7-2and PH6WC×zheng58as basis materials in60000plants/hm2,90000plants/hm2,120000plants/hm2,150000plants/hm2under selection pressure, S3generation were selected five representative departments and four critically excellent inbred lines forming NCII and identified the best selection density by analysing the production performance and the combining ability. On the base of zheng58xPH6WC, F2, F3and F4were selected under density of12000plants/hm2and S3generation were selected five representative departments and four critically excellent inbred lines forming NCII and identified the best selection generation by analysing the production performance and the combining ability. The fourth, under three densities including60000plants/hm2,75000plants/hm2and90000plants/hm2, heterosis and combining ability of maize were analysed and their changing regularity was also researched. Above researches provided theoretical references for breeding under high density.1. Aalysis on density-tolerance of maize inbred linesIn five densities, empty stem(0), double ears(12.3%), ASI(1.36d), ear tip length(0.61cm), yield per ha were advantage characters for Chang7-2. The density-tolerance of Chang7-2was the best. The lodging resistance(0), double ears(5.9%), empty stem(1.1%), ASI(1.95d) and yield per ha were advantage characters for Zheng58. The double ears(9.2%), empty stem(1.07%), ASI(1.67d) and yield per ha were advantage characters for PH4CV. The density-tolerance of Zheng58and PH4CV was better. The double ears、empty stem and ASI of PH6WC were0.56%,38.9%,2.93d respectively, The double ears、empty stem and ASI of Mo17were0.13%,6.1%,2.96d, respectively. The double ears、empty stem、ASI and ear tip length of Dan340were 0,26.8%,4.13d,2.57cm, respectively. The density-tolerance of PH6WC and Dan340was bad.2. Analysis on density-tolerance of maize hybridsThe best yield density was75000plant per ha in Zhengdan958under the model of improved ReidxTangsipingtou.The short eartip, the low rate of empty stem and lodging for the hybrids under the above model, which showed the better density-tolerance. The best yield density was60000plant per ha in Xianyu335under the model of ReidxLancaster.It was not suitable to close planting for the hybrids who had the high rate of empty and lodging under the above model. The best yield density was60000plant per ha in Nonghua101under the model of USA-hybrid xLvdahonggu. The hybrids had potential on the low short eartip, the low rate of empty stem and lodging for closing planting. The best yield density was90000plant per ha in Limin33under the model of Abroad-hybridxLvdahonggu. It was suitable to close planting for the hybrids who had the low short eartip,low rate of empty and lodging under the above model.3.Analysis on the best selection density for inbredlineAll the GCA effects of inbred breeding from PHBlMxChang7-2in12000plants per ha were positive and the variation scope of SCA was small. The number of high yield hybrid more than other density.12000plants per ha was the best selecting density of inbred lines for PHB1M×Chang7-2. All the GCA effects of inbred breeding from PH6WCxZheng58in90000plants per ha were positive and the variation scope of SCA was small. The number of high yield hybrid more than other density,90000plants per ha was the best selectiong density of inbred lines for PH6WCxZheng58. All the GCA effects of inbred breeding from F2of PH6WCxzheng58were positive and the variation scope of SCA was small. The number of high yield-hybrids more than other densities, using F2of PH6WCxzheng58as basis material was the best for selecting lines under high density.4. Analysis on heterosis, combining ability and gesnetic parameterThere were differences between the heterosis of different combinations under the density conditions, which decreased with the increasing of density. There were obvious differences between the traits of the selected and main inbred lines in GCA effects under the different density conditions.What’s more,the traits of the same inbred lines in SCA effects showed differences in different density conditions t. Meanwhile, it was inconsistent in the combination of SCA effects changed with density increased. Hereditary for plant height, ear, ear length, rows per ear, kernel weight mainly to the role of additive effects, yield per plant and ear tip length mainly to the role of non-additive effects. Plant height, ear, ear length, grain length, rows per ear, kernel weight of selection should be in the early generations, rows per ear and yield per plant in the late generations.